During the past decades, hemodialysis apparatus have achieved a high level of development and are used routinely in the treatment of patients with kidney diseases. The principle construction of a hemodialysis apparatus is known from German Patent No. 2,838,414.
In the case of hemodialysis apparatus that are designed as single-place or single-station units and are set up in a kidney patient's house, the dialysis fluid is sucked from canisters or merely a dialysis solution concentrate is sucked from a canister and then is mixed with water in the dialysis apparatus in order to produce the dialysis solution required for use in the machine. On the other hand, in hospitals with multiple dialysis stations or places, it has become the state of the art to connect each dialysis device by means of a connector to a supply conduit, embodied as a loop conduit. Such an arrangement or construction of a multi-station apparatus for the simultaneous treatment of multiple patients is known from European Patent Application No. 0,052,008.
In such a manner, the supply loop conduit can either supply a completely prepared dialysis fluid to the individual hemodialysis apparatus, or can merely supply individual components of the dialysis fluid, which is to be mixed in the dialysis apparatus, such as acid and bicarbonate for example. Especially in the latter case, it can also be that several supply- or ring-conduits are provided which deliver separate components, whereby an appropriate number of branch conduits flow from each ring conduit to each individual dialysis apparatus.
The supply conduit is usually connected to the dialysis apparatus by means of a connector, for example in the form of a coupling or the like. In this context, at least a (first) shut-off device is provided in the conduit portion from the supply conduit to the individual components of the dialysis apparatus, in order to prevent a backflow of fluid into the supply conduit. It is especially important to prevent such a backflow when the hemodialysis apparatus and the entire conduit system contained therein is being rinsed or flushed out with a cleaning and/or disinfecting solution, which is usually carried out after every treatment. If it enters the supply conduit, the comparatively strong or aggressive cleaning and disinfecting fluid can be carried to other dialysis apparatus connected to the conduit, thereby possibly resulting in a life-threatening situation if a dialysis treatment is being carried out on the other apparatus at the time.
While a backflow of fluid out of the conduit system of a dialysis apparatus into the supply conduit could be prevented by means of a simple non-return valve, it is furthermore desirable that no dialysis fluid flows out of the supply conduit into the conduit system of the dialysis apparatus during the cleaning of the dialysis apparatus, because a mixing of dialysis fluid and cleaning fluid can lead to reactions, which could damage the dialysis apparatus.
In order to solve this problem, it has been customary in dialysis apparatus according to the current state of the art, to install a magnetically controlled valve instead of a simple non-return valve in the conduit portion between the supply loop conduit and the dialysis apparatus.
In such an arrangement, the magnetic valve closes or blocks the conduit portion between the loop conduit and the dialysis apparatus in both directions and thus prevents a flow of fluid. However, because a backflow of disinfecting fluid into the supply conduit would be hazardous to people's lives, and thus by all means must be prevented, it is necessary to immediately detect any failure of the magnetic valve closing off the conduit. For safety reasons, therefore, the dialysis apparatus is separated from the loop conduit during the disinfection so as to be able to immediately detect any potentially occurring leakage of the magnetic valve and to reliably prevent a backflow of disinfecting fluid into the supply loop conduit carrying dialysis fluid.
Separating the hemodialysis apparatus from the supply conduit is, however, time consuming, expensive and moreover inconvenient for the hospital staff. Thus, on the one hand, costly losses of time can occur because the useful operating time of the hemodialysis apparatus is reduced, and on the other hand, the hospital staff may be tempted to dispense with separating the dialysis apparatus from the supply conduit in reliance upon the proper functioning of the magnetic shut-off valve, whereby the intended high safety standard is reduced.